Transition from coaxial cable to a ground-symmetric device supplied thereby



Oct. 13, 1959 A o. ZINKE ET AL 2,908,876

A TRANSITION FROM COAXIAL CABLE TO A GROUND-SYMMETRIC DEVICE SUPPLIED THEREBY Filed June 21, 1956 2 Sheets-Sheet 1 Oct. 13, 1959 o. ZINKE ETAL 7 2,908,876

TRANSITION FROM COAXIAL CABLE TO A GROUND-SYMMETRIC DEVICE SUPPLIED THEREBY 2 Sheets-Sheet 2 Filed June 21, 1956 ll/ I Fig.6.

United States Patent TRANSITION FROM COAXIAL CABLE TO A GROUND-SYMMETRIC DEVICE SUPPLIED THEREBY Otto Zinke and Peer Thilo, Darmstadt, and Wolfgang Krueger, Munich, Germany, assignors to Siemens & Halske Aktiengesellschaft, Berlin and Munich, Germany, a corporation of Germany Application June 21, 1956, Serial No. 592,941

Claims priority, application Germany June 30, 1955 4 Claims. (11. 333-26) This invention is concerned with an arrangement for effecting transition from a coaxial cable to a ground-symmetric device supplied thereby.

The problem is often posed to feed ground-symmetric apparatus over a coaxial cable. A symmetrizing device may in a well known manner be used for this purpose, wherein the inner and outer conductors of a coaxial cable are connected to a tube system comprising parallel branches, the inner conductor of the coaxial cable extending through one branch, leaving such branch at the other end and being connected with the corresponding end of the other branch. The ground-symmetric apparatus is in such device connected to the two ends of the tubular branches.

The object to feed a ground-symmetric arrangement over a coaxial cable must be extended in many cases as the' corresponding arrangement may be a rhomboid antenna having an impedance exceeding the wave impedance of the coaxial cable.

Arrangements are known providing for symmetrizing and also for transforming; In one of these arrangements, the symmetry is obtained according to the above mentioned known scheme and the transforming from the characteristic impedance of the coaxial cable to the impedance of the apparatus fed thereby is realized byan exponential line.

The drawback of the known arrangements is primarily that they require considerable space, particularly for the exponential line.

The object of the invention is to carry out symmetrizing and transforming with satisfactory wideband characteristics while requiring very little space as compared with known arrangements. The arrangement according to the invention is accordingly advantageously used in many cases requiring space saving construction.

According to the invention, in an arrangement for the transition from a coaxial cable to ground-symmetric apparatus fed thereby, which has an impedance exceeding the characteristic impedance of the cable, the cable is connected to a central point of a coil made wholly or partially of tubes, the connection being such that the outer conductor of the cable is connected with the tubular coil body while the inner conductor is carried through the coil convolutions of one half of the coil to a point opposite the corresponding coil end, the inner conductor extending through a wall of the coil and being conductively connected with a point of the other half of the coil which is disposed symmetrical to the exit point. The ends of the coil windings which extend beyond these points which are of a length to afford the required transforming, are connected with the ground-symmetric arrangement fed by the coaxial cable.-

In order to compensate for the capacitance or inductive impedance component produced by the transforming, it is of advantage to provide an auxiliary capacitance at the connecting point of the coaxial cable between its 2,908,876 Patented Oct. 13, 1959 5 geously formed by providing an inner conductor within the tubular parts of the coil which are free' of the inner conductor of the coaxial cable.

The cross sectional shape of the tubular windings may be of various forms, for example, circular, elliptical or rectangular. The convolution of the coil windings may likewise be of various configurations, as for example, conforming to cross-sectionally differently shaped mandrels.

The foregoing and other objects and features of the invention will now be described with reference to the accompanying drawings wherein Fig. 1 shows a known symmetrizing device;

Figs. 2 to 4 are schematic representations of embodiments according to the invention;

Fig. 5 is a perspective view of a particularly advantageous embodiment; and

Fig. 6 is a section along line 66 of Fig. 2.

In the well known arrangement shown in Fig. 1, there is a coaxial cable comprising an inner conductor 1 and an outer conductor 2. These conductors are connected with a tube system comprising branches 3 and 4, the inner conductor of the coaxial cable being carried through the branch 3 and leaving such branch at its open end 5 and being connected with the end 6 of the branch 4. The ground-symmetric apparatus is connected to the ends 5 and 6 of the tube branches 3 and 4.

In Fig. 2, the outer conductor 2 of the coaxial cable is connected with the outer conductor at the connecting point of the tubular coil halves 3 and 4. The inner concluctor is carried through the coil half 3, inside thereof, to the point 10, where it is carried to the outside and connected with a point 11 of the other coil half 4 which is symmetric to the point 10. The coil convolutions extend beyond the points 10 and 11 according to the required transforming of the characteristic impedance of the coaxial cable to the impedance of the device fed thereby. The terminal points 12 and 13 of the coil halves 3 and 4 are connected with the ground-symmetric device fed by the cable.

The coil parts lying respectively between the points between the points 10 and 11; they may be solid throughout, and the cross sectional shape thereof need not correspond to that of the parts extending between points 10 and 11. i

Fig. 3 shows in perspective view an advantageous symmetrizing and transforming arrangement. The coil parts between points 10 and 11 of Fig. 2 are in this embodiment formed by two annular tubes 3 and 4. The coaxial cable comprising the inner conductor 1 and the outer conductor 2 is connected to one end of the tube 3 in such a manner that the outer conductor 2 merges with the tube 3, the inner conductor 1 being carried through the tube 3 inside thereof and leaving such tube at a point 10 coinciding with the end of the corresponding tube. Point 10 corresponds to like numbered point in Fig. 2. The inner conductor leaving tube 3 at point 10 is connected with one end (inlet) of tube 4. The other end of tube 4 is connected with the inlet end of tube 3 by means of interconnecting line 7 so that the tubes 3 and 4 form in eifect a continuous coil. The extension of the coil winding formed by the tubes 3 and 4 beyond points 10 and 11, which is for convenience indicated by arrows 15 and 16, must correspond to the required transforming between the characteristic impedance of the coaxial cable and the ground-symmetric impedance of the apparatus fed 3 thereby. The end points of the coil extensions 15 and 16 are connected with the apparatus or device fed by the coaxial cable. The extensions of the coil windings beyond the points 10 andll may be formed by thin wires or other members of desired profile.

As is known, inductive or capacitanceimpedance components occur in the transformation to be considered here. Such components may be compensated by suitably disposed capacitances extending, for example, in parallel to the connecting points of the coaxial cable and/or between the inner conductor carried outside at point It) and the outer conductor. In the arrangement according to Fig. 3', this compensating capacitance may be realized in particularly simple manner by the provision inside of the tube 4 of an inner conductor of suitable length and thickness and connecting such inner conductor with the portion of tube 3 surrounding the point 10. The corresponding arrangement is indicated in Fig. 4, showing an auxiliary inner conductor within the tube 4 which is connected with tube 3 by means of a connecting line 8.

The capacitances serving for the compensation of the inductive impedance components. may also be realized carrying out alterations of the characteristic impedance of the coaxial cable, at suitable points, and/ or by alterations of the line represented by the tube 3 and its inner conductor. Another possibility to compensate the inductive or capacitance component occurring in the transforming is to provide a series capacitance in the course of the connected input line (coaxial cable with the inner conductor 1 and outer conductor 2).

In order to keep the stray or leakage inductance occurring in the arrangement according to the invention as small as possible, it will be advantageous to arrange the coil convolutions close one to the other. Ferromagnetic materials may under some conditions be suitably used for the coil core.

Fig. shows a particularly advantageous structure of the arrangement according to the invention. The coil windings or convolutions which are secured together by a plurality of clamping members are held at one point rigidly and at one or more points resiliently within an in sulating casing made preferably of an artificial glass-fiber material. The mounting tube containing the coaxial input cable is embedded in the casing. Fig. 5 illustrates an insulating casing 21 made preferably of an artificialglass-fiber material, and a mounting or lead-in tube 22 containing the coaxial cable 23.

The coil convolutions made in part of tubes 24 and in part of solid members 25 are held mechanically rigidly at point 26 and resiliently at two points 27' and 27". The position of point 27 is indicated by an arrow because it is not visible in the drawing. The windings or convolutions are held together by insulating clamps 28 to form a structural unit. The ends of the secondary windings are connected with terminals 31 by means of leadthrough insulators 30. The ground-symmetric device fed by the coaxial cable is connected to the terminals 31. An air filter 32 is provided for atmospherically dustfree pressure equalization within the casing.

Changes may be. made within the scope and spirit of the appended claims.

We claim:

1. An arrangement for effecting transition from a coaxial cable including an inner conductor and an outer conductor to a ground-symmetric device supplied thereby comprising an impedance exceeding the characteristic impedance of said coaxial cable, said arrangement comprising a coil having two symmetrical halves, each half having a terminal portion disposed at the center of said coil connected to the outer conductor of said coaxial cable, at least one of the coil halves'having a tubular portion extending to its said terminal portion, an internal conductor within said tubular portion having a terminal disposed at the center of said coil connected to the iimer conductor of said coaxial cable, said internal conductor being of less length than the half of said coil in which it is positioned, said internal conductor emerging in insulated relationship from an intermediate point of its coil half and being conductively connected to the other of said coil halves at a point disposed symmetrically about said center to the point of emergence, and each half of said coil having a terminal electrically remote from said coaxial cable providing connections to a groundsymmetric device.

2. An arrangement according to claim 1 comprising means forming an auxiliary impedance comprising a conductor connected to said one coil half adjacent said point of emergence and extending through the other of said coil halves adjacent said symmetrically disposed point in coaxial fashion towards said center.

3. An arrangement according to claim 1 wherein said coil halves are tubular and rectangular in cross-section.

4. An arrangement according to claim 1 comprising a casing, insulating clamp means for holding said coil halves, means for rigidly securing said coil halves within said casing at one point, and means for resiliently securing said coil halves within said casing, and a tubular lead-in member embedded in said casing for conducting therein to said coaxial cable.

References Cited in the file of this patent UNITED STATES PATENTS 2,777,996 Bruene Jan. 15, 1957 

